According to the service manual, part number is ASE-105
Can't find it anywhere either. Usually entering a part number on google leads to part websites, but i can't find anything for ASE-105. So maybe you should look after parts or defect pioneer receivers/amplifiers on ebay, they are usually cheap. Multiple models use those kind of switches.
I'm myself looking after lever switches for SA-9500II / SA-8500II. Parts number ASK-110, ASK-109 & ASK-113. Hard to find.
I'll post an answer here if i ever find a good source for parts.